Photographic reversal process



. Patented Mar. 23, 1943 PHOTOGRAPHIC nEvEnsAi. rnocsss v James B. Alburger, Merlon, Pa... assignor to Rs.-

dio Corporation of America Delaware 'a corporation of No Drawing r Application May 31, 1949,

' Serial No. 338,051

7 Claims.

This invention relates to a photographic reversal process particularly adapted for use with motion picture film and more specifically adapted for use with ordinary positive types of film for taking the original picture and producing the reversal print. V

In the practice of the production of positive pictures by the reversal process, as customarily applied, for example, to the production of 16 mm. and 8 mm. motion pictures, a specially coated type of film is used for the reason thatthe pictures of average subject matter a rating of 16 may be used for this film when developed ac- I cording to my process, and for scenes having conreversal processes heretofore employed failed to give either'clear whites or proper gradation when applied to ordinary types of film.

In the present process it is possible to use ordinary positive motion picture film --for' the original exposure and to produce perfectly satisiactory positives therefrom and with thispositive film showing an effective speed of from 10' to 30 times that which it ordinarily shows when developed according to the customary methods. The improved process further prevents to a large extent the reticulation which often occurs in the application of reversal processes? In the performance of my improved process I use a hardening developer of the general type de-' scribed and claimed in my Patent No. 2,199,904, thereby preventing reticulation, and by overdeveloping somewhat and partially dissolving the silver salts in the image I secure the proper residual amount. of silver for the production of the positive image. .Y One object. of the invention is to provide an improved photographic reversal process.

Another object of the invention: is to provide a photographic reversal process whichfipermits the use of positive film.

Another object of the invention is to provide a photographic reversal process which greatly increases the effective speed offilm used;

Other and incidental-objects of the invention will be apparent to this skilled in the art from a reading of the i owing specification.

' In the preferre manneroi performing my process,I use an ordinary positive motion pic ture film. One type ofsuch film which is appropriatefor the purpose is that known commercially as EK 1301 although any equivalent positive film'stock may be used as desired, for example, 'the type known as Dupont Micro-Pan is quite satisfactory.

-In the exposure of the iilmia speed ratingof irom to 80 times the normal speed ratingis giveir'to. the firm. For example. the EK'1301 film is normally'rated at watch 1, while for developer having preferably the following compotion: I

Metol l "grams..- 4 Sodium --su lphite do 120 Hydroquinone do 8. 5 Potassium alum ....do

,Potassium bromide do'.... 8 Sodum hydroxide do Water -e --cc 1000 It will be obvious that the composition of the.

siderable sky or water in them a rating as high as 32 may be used for the same film. The effective ratings for other types of film vary correspondingly.

After exposure, the -iilm" is developed, for example, for 13 minutes at 65 Fahrenheit in a developer may be varied considerably within the '0 scope of theinvention but there .are a few feaquinone maybe .tomary according to the typeof contrast that is tures which must be kept substantially the same in such variation.

potassium alum main practically constant, as described and claimed in my Patent No. 2,199,904, referred to above, and the proportion of sodium sulphite must be kept high in order to effect the necessary solvent action on the silversalts in the emulsion.

The potassium bromide may be varied considerably but the quantity suggested above is that which produces the least variation in the die t of the developer with use. The proportions d quantities, of the Metol -(or Elon) and hydrovaried considerably as is cusdesired.

In the preparation of the developer the potas-x slum alum will not completely dissolve until the sodium hydroxide is added. A gelatinous suspension is formed which is harmless but which a hardening bath'which may have thei'ollow- -ing composition:

may be filtered'ofi, if desired. Afterthedevelopment the film should be rinsed in running water for about 30 seconds and then hardened in After hardening .i'or one or two minutes the film should be rlnsed, and then bleached in an The relation between the and sodium hydroxide must re- I open:

appropriate bleaching bath lowing is typical:

20 Sulphuric acid concen.. cc 20 -Water.-' do 1000 er, the bleaching is complete the film should be rinsed and then cleared in a bath of 10 percent sodium sulphite in water.

After 1 clearing the mm should be washed thoroughly for at least 3. to 5 minues in order to prevent any stain appearing during the second development. The film is then completely exposed and then developed in the second devel- This second developer may be the same as the" first developer or it may be any ordinary type developer.. One developer which is desirable for this purpose is that which is generally known as D 76, which produces a slightly finer grain structure in the final developed image than some of the other developers available.

The. first developer which contains considerable alum prevents undue swelling of the emulsion during the development in spite of the large quantity of alkali used. Also, as described in my patent above referred to, the balance between the alum and alkali serves to stabilize the developer and prolongs its useful life to such an extent that it may be completely carried away by the film being processed before it is chemically exhausted.

The bleaching bath usually tends to produce considerable reticulation and this is prevented not only by the nardening developer but by the includes developing a silver halide emulsion in a. developer containing balanced amounts of alum and alkali and a quantity-of sodium sulphite approaching saturation, bleaching the film, exposing and redeveloping.

2. The method of producing reversal prints including the steps of developing a silver halide emulsion in a developer containing balanced amounts of alum and alkali and sodium sulphite hyde, hardens the film to such an extent as to 1. The reversal print producing method whichapproaching saturation, hardening the emulsion, bleaching the image, exposing and redeveloping.

3. The method of producing reversal silver halide emulsion prints comprising the steps of exposing a positive type film;- developing the film in a developer containing balanced amounts of alum and alkali and'a quantity of. sodium sulphite approaching saturation, bleaching the film, exposing and redeveloping.

4. In the production of reversal silver halide emulsion photographic images, the step including the development of the original image in a developer containing balanced amounts of alum and sodium hydroxide and silver sulphite approaching saturation.

5. In the production of reversal silver halide emulsion photographic images, the step including the development of the original image in a developer containing balanced amounts of alum and sodium hydroxide and a quantity of sodium sulphite approaching saturation. I

6. A photographic developer of silver halide emulsions including a developing agent, balanced amounts of alum and sodium hydroxide and a quantity of sodium sulphite approaching saturation.

'7. A photographic developer having substantially the following composition: 1

Metol grams 4 Sodium sulphite do 120 Hydroquinone do 8.5 Potassium alum ..-do 40 Potassium bromide do 8 Sodium hydroxide do 30 Water cc 1000 JAMES R.- ALBURGER. 

